1. Field of the Invention
The present invention relates to a battery accepting unit for a battery operated electric/electronic apparatus, such as a portable computer, and to a battery pack; and in particular to a battery accepting unit which can exchangably install a battery pack, and a battery pack. More specifically, the present invention pertains to a battery accepting unit that permits the exchange of a battery pack without halting the power supply to an electric/electronic apparatus, and to a battery pack.
2. Description of the Related Art
As a consequence of recent technical developments, for which portability and outdoor use were important considerations, compact and light electric/electronic apparatuses have become popular. So-called "notebook computers" are good examples.
In FIG. 20 is shown the outline of a notebook computer (hereinafter referred to simply as a "PC" or a "system") 100. This structure is substantially the same as a computer disclosed in Japanese Design Application No. Hei 06-30003 (Our docket No.: JA9-94-621), which was assigned to the present applicant. The PC 100 has a so-called "structure with a lid" constituted by a thin main body 110 and a lid 120 which is pivotaly hinged on the main body 110.
The lid 120 has a shallow upper case 121. A pair of cylindrical protrusions 122 are integrally formed at the lower edge of the upper case 121, and are rotatively supported by the main body 110, so as to hinge the lid 120 with the main body 110. A liquid crystal display (LCD) 123, the display means for the PC 100, is provided substantially in the center of the opened face of the upper case 121 (i.e., the reverse side of the lid 120). The lid 120 can be opened and closed relative to the main body 110 by sliding forward and backward operating portions 124 that are formed at the front on either side of the upper case 121.
The main body 110 has a shallow lower case 111. A support board 112 having a predetermined size is provided on the lower case 111 to cover the rear portion of an upper opening in the case 111. A keyboard/TrackPoint 113 ("TrackPoint" is a trademark of IBM Corp.) is provided substantially in the center of the upper opening to serve as an coordinate pointing means for the PC 100. A pair of loudspeakers 114 for audio output are provided at the right and left corners at the front of the keyboard 113. A pair of cylindrical tongue pieces 115 that are integrally formed at the rear edge of the keyboard 113 pivot at the front edge of the support board 112, hinging the keyboard 113 with the support board 112 and permitting it to be opened and closed. An indicator 117 is provided on the hinged portion at the rear end of the lower case 111. The indicator indicates the remaining capacities of a battery, the state of a PC card, the state of a floppy disk drive (FDD) and of a hard disk drive (HDD), and the status of the system 100 when the power is on.
In FIG. 21 is shown the internal structure of the main body 110 when the lid 120 and the keyboard 113 of the PC 100 are opened. A partition wall 116, which defines a front chamber and a rear chamber, is provided in the lower case 111. The partition wall 116 is formed by bending a thin metal plate into a predetermined shape. In the rear chamber, which is hidden by the support board 112 and the partition wall 116, are stored a system board (not shown), on the surface of which are mounted essential electric components, such as a CPU (Central Processing Unit), a system memory, a memory controller, a ROM, a video controller and an audio controller. This rear chamber is relatively narrow and the installation density for the electric components mounted in this chamber is very high. Into the front chamber, forward of the partition wall 116, input/output devices, such as an HDD pack 117 and a CD-ROM drive 118, and a battery pack 119 as a main power source, are detachably accommodated. Several connectors (not shown) are provided on the front side of the partition wall 116 for mechanically and electrically coupling the terminals of the HDD pack 117, the CD-ROM drive 118 and the battery pack 119.
One of the features of such a portable personal computer is that since the surface area of the box (the lower case 111) is very small, the number of openings and connectors that are provided for attachment/detachment and removal of I/O devices is limited. For example, as is shown in FIG. 20, a drawer for exchanging a CD employed as a storage medium is formed in the front of the main body 110; an exchanging opening 132 for the insertion of the battery pack 119 is formed in the right side of the main body 110; and a PC card slot 133 for inserting a PC card (two Type .sub.-- /.sub.-- cards or one Type .sub.-- card) and an I/O port 134 for an external port for an external keyboard/mouse (not shown) are provided in the right side near the back of the main body 110. As is shown in FIG. 22 at the rear of the main body 110, a jack 135 for attaching a connector for an external power supply (an AC adaptor) is provided in an opening, and a serial port, a parallel port, a CRT port and a SCSI port are provided in a recessed portion and are protected by a hinged door 136. Further, as is shown in FIG. 22, in the left side of the main body 110 are formed a connector 137, for mounting an expansion adapter card that is pin-compatible with an ISA bus (Industry Standard Architecture bus; one of the input/output buses in the PC 100), and a power switch 138. In short, many devices vie for the narrow surface of the box of the PC 100. If more openings and connectors are formed, the mechanical strength of the box may be deteriorated.
Another feature of such a portable personal computer is that it is designed for a "battery operation type" using an incorporated battery, so that it can be used in places where AC power is not available. In order to supply sufficient power to the system, for the incorporated battery as a "battery pack" is used wherein a plurality of battery cells connected in series or in parallel are assembled together to form a package (e.g., the battery pack 119 in FIG. 21). Since such battery packs must be used repeatedly, rechargeable battery cells, such as those made with NiCd, NiMH or Li-Ion, are employed.
It would be easily understood that while the external AC power source is almost infinite, the capacity of a battery pack is finite. For example, a fully charged battery pack for a notebook computer supports an operating period for a PC of only two or three hours. And though this period may vary, depending on the PC model and the used conditions, the charge on the battery pack will become exhausted while the PC is in use, and the battery pack will have to be replaced by a new (or recharged) one.
Many volatile components, such as system memory and video RAM constituted by DRAM, are included among the memory devices in a PC. When the power supply is cut off, even for a moment, while the PC is in use, data currently being employed, or a file that has been completed and is being held in the volatile memory device, will be lost and will not be recoverable. As a result, a user must repeat the performance of a task from the beginning.
Such data loss will also occur when a battery pack is replaced. To cope with this problem, many battery operated electric/electronic apparatus include a relatively compact auxiliary battery (or a "sub-battery") that provides backup support only for the short period of time required to change a main battery. A portable electric/electronic apparatus that has a subsidiary power source equivalent to a sub-battery is disclosed in, for example, Japanese Examined Utility Model Publication No. Sho 63-27357, Japanese Examined Utility Model Publication No. Hei 07-4662, and Japanese Patent Application No. Hei 05-130749. In FIG. 23 is shown a conventional schematic arrangement for a power supply system in a notebook computer 100 that also employs a sub-battery.
In FIG. 23, an AC adaptor 201 converts a voltage (generally AC 100 V) input by an AC power source into a DC voltage. A battery pack 202, which is incorporated in the PC 100, consists of a plurality of battery cells, and supports a two to three hour operating period for each full charge. A circuit 203 selectively transmits the power supplied by the AC adaptor 201 and the battery pack (hereinafter also referred to as a "main battery") 202, and charges the main battery 202 using the power supplied by the AC adaptor 201. When both the AC adaptor 201 and the main battery 202 are connected to the circuit 203, the circuit 203 gives priority to the power supplied from the AC adaptor 201. A main DC/DC converter 204 reduces a DC voltage received from the AC adaptor 201, or the main battery 202, to an appropriate voltage level that the system 100 can use. A sub-battery 206 is an auxiliary for the main battery 202, and is used to back up a volatile memory in the system 100 only in a short period of time while the main battery 202 is being replaced. In response to the need to save space and to lower manufacturing costs, the sub-battery 206, as designed, is a compact power source consisting of, for example, three rechargeable NiCd or NiMH coin batteries, and has a power capacity that can support for a system 100 that is operating in a low-power consumption mode (a so-called suspend mode) for only three minutes. A circuit 207 is the charging circuit for the sub-battery 206, and a circuit 208 controls selective charging and discharging of the sub-battery 206. A sub-DC/DC converter 209 generates the voltage which can be used by the the system 100 during the discharging of the sub-battery 206, and a circuit 205 selectively supplies, to a system load 211, voltages output by the main DC/DC converter 204 and the sub-DC/DC converter 209. The system load 211 is the electric circuit in the system 100 that actually consumes power, and includes a CPU, a system memory, an HDD and a CD-ROM drive. A power management processor 210 is a specific processor for controlling the power flow from the power sources 201, 202 and 206. The power management processor 210 monitors the operating state of the system load 211, and outputs control signals to the blocks 203, 204, 207, 208 and 209. The primary controls of the power management processor 210 (1) give priority to the power supply from the AC adaptor 201 rather than from the main battery 202; (2) switch between the charging and the discharging of the main battery 202 and the sub-battery 206; (3) permit the charging of the main battery 202 and the sub-battery 206; and (4) supply power output by the main DC/DC converter 204 during normal operation, switching to the power supply output by the sub-DC/DC converter 209 only while the main battery 202 is being exchanged.
As is shown in FIG. 23, a power supply system that includes a sub-battery has already been adopted for use in, for example, the ThinkPad series ("ThinkPad" is a trademark of IBM Corp.), sold by IBM Japan, Ltd.
As is described above, a sub-battery compensates for the period during which the power supply from a main battery is cut off. However, when an electric/electronic apparatus is equipped with a sub-battery in addition to a main battery, the following problems have arisen.
(1) A power supply system other than a main power source (the AC adaptor 201 and the main battery 202) must be provided for the electric/electronic apparatus. Accordingly, an extra circuit for the sub-battery 206 is required. In the block enclosed by the broken lines in FIG. 23 are described additional components that accompany the inclusion of the sub-battery 206. These components constitute additional burdens imposed on the design of a notebook PC for which the requirements of small size, small weight and low manufacturing costs are considerations. Since the power management processor 210 has to drive the additional block, a program for this purpose is also complicated. PA0 (2) The capacity of the sub-battery 206 is extremely small. In the previously mentioned ThinkPad series, the power is supplied by the sub-battery 206 only in the low-power consumption mode (suspend mode). During the exchange of the main battery 202, the system 100 should be switched to the low-power consumption mode (suspend mode) manually by an operator, or automatically, and is backed up by the sub-battery 206. If an operator forgets to switch to the suspend mode, or if the exchange of the main battery 202 takes more time than expected and the charge on the sub-battery 206 is exhausted, data loss occurs. And in any event, there is some possibility that data loss will occur when the parallel employment of a main battery and a sub-battery has been adopted.
Several battery exchange methods have been proposed whereby the power supply is not cut off even when a sub-battery is not used. An apparatus/system for exchanging a battery without halting the power supply is disclosed in, for example, Japanese Unexamined Patent Publications No. Sho 61-135050, No. Sho 61-250965, No. Hei 02-61959 and No. Hei 04-286860, Japanese Unexamined Utility Model Publications No. Sho 59-141652 and No. Sho 59-146861, and Japanese Examined Utility Model Publication No. Hei 04-19715.
Most of the apparatuses/systems disclosed in these publications are slide-through systems whereby a new battery is pushed in at one end of a battery storage room and an old battery is discharged from the other end. The positive and negative poles of the new and the old batteries slide along the common electrodes of the electric/electronic apparatus before the replacement is completed, so that the power supply is not halted.
In such a slide-through system, however, the insertion and extraction openings for new and old batteries must be provided in the surface of the PC. Unlike an apparatus that has extra storage space, for a notebook PC, many components vie for openings in the surface of the case, as previously described, and it is not realistic to prepare two openings for battery packs. If a new opening is formed, the mechanical strength of the case will be deteriorated. Further, room through which the new and the old battery packs are passed is required, and the sharing of a space that is larger than the footprint of the battery pack is not permitted for a case wherein the components are as crowded as is shown in FIG. 21.
Since the old battery having a low terminal voltage and a new battery having a high terminal voltage slide along the common contact pieces, this causes a short-circuit during which a large current flows from the new battery to the old battery and both batteries may be damaged. In the above described publications, however, that a short-circuit occurs between the batteries is neither pointed out nor is the issue resolved.